Over-the-road land vehicles such as trailers, vans and trucks typically have a roof skin and side wall skins that are supported by metal frame structure. For brevity, as used herein, all such over-the-road land vehicles will be referred to as trailers. Specifically, the metal frame structure includes a plurality of side wall posts that support top rails that extend on opposite sides along an axial length of the trailer. At spaced apart intervals along the length of the trailer, a plurality of roof bows extend laterally between the top rails. The metal side wall skins are riveted to the side wall posts and the top rails. The roof skin is supported by the roof bows and riveted to the top rails. The roof skin is adhesively attached to the bows.
A roof bow typically includes an elongated channel with a pair of clips or end pieces affixed to opposite ends of the channel. The end pieces include a plurality of openings adapted to be fastened by rivets or other fasteners to aligned openings in the top rails.
Since the bows span the side rails it is important that the overall length of the bows be maintained within narrow tolerances in order to insure that the top rails run parallel along the axial length of the trailer. Because significant forces are applied to the roof bows when the trailer is loaded and driven over the road, it is important that the end pieces are securely affixed to the channel so that the bow is strong and durable. Finally, to minimize production costs, it is important that the fabrication process for affixing the end pieces to the channels be efficient.
Various methods have been used to fix end pieces to channels including welding, riveting and coining. Each method has its disadvantages. Welding is expensive because of the manual effort and skill level required for welding. Riveting also has a high cost because of the cost of the rivets and the cost associated with drilling or punching of aligned holes in the end pieces and the channel to accept the rivets. Coining involves punching holes in the channel end portion, extruding smaller diameter holes in an end piece, aligning the end piece extruded holes with the channel holes and coining out the end piece extruded holes to attach the end piece to the channel. While coining is less expensive than riveting or welding, it still requires holes to be punched in both the channel and the end piece. Additionally, extruding holes in the end piece tends to wear the end piece dies out rapidly.
What is needed is a method of manufacturing roof bows that is cost efficient, results in a strong and durable coupling between the end piece and the channel and consistent bow length between successive bows.